Nunit、NCrunch 和 NSubstitute - 总是有 2 个测试因 UnexpectedArgumentMatcherException 失败，随机变化（准）

Question

我有一个使用 NUnit 3.4.1、NSubstitute 1.10.0 和 NCrunch 2.23.0.2 的文本夹具

此夹具中的任何时间点都有 2 个失败的测试。每次我更改某些内容时，哪个测试失败似乎都会有所不同。并非所有测试最终都会失败，但大多数都会失败，而且问题始终是 NSubstitute 异常，如下所示：

// _clock is initialized as _clock = Substitute.For<IClock>();
// the dates in the Returns statement change on every test
_clock.Now.Returns(new DateTime(2015, 1, 1));

我将 NCrunch 添加到此组合中，因为 Resharper 2016 测试运行器似乎通过了所有测试。大部分。

我总是得到的例外是：

NSubstitute.Exceptions.UnexpectedArgumentMatcherException : Argument matchers 
    (Arg.Is, Arg.Any) should only be used in place of member arguments. 
Do not use in a Returns() statement or anywhere else outside of a member call.

这很清楚，除了在大多数测试中我不使用任何Arg.Is 或Arg.Any。

IClock接口

这是IClock 界面，尽显其荣耀。 Now 是一个 getter-only 属性，但这对 NSubstitute 来说应该不是问题，不是吗？

public interface IClock
{
    DateTime Now { get; }
}

整场比赛，即将到来

很抱歉出现大量代码，但我不想假设这是由于一个测试或另一个测试，所以这里是：

[TestFixture]
public class AuctionTests : TestBase
{
    #region Fields

    AuctionService _auctionService;
    IClock _clock;
    Ride _ride;
    IMailService _mailer;

    #endregion

    [SetUp]
    public void Init()
    {
        _clock = Substitute.For<IClock>();
        _mailer = Substitute.For<IMailService>();

        _ride = new Ride
        {
            StartAuction = new DateTime(2016, 2, 12, 19, 0, 23),
            PriceForCustomer = 20m,
            InitialAuctionPrice = 15m,
            HighestAuctionPrice = 19m
        };

        SetupData(_ride);

        _auctionService = new AuctionService(RavenSession, _clock, _mailer);
    }

    [Test]
    public void Auction_rejects_price_when_price_is_higher_then_HighestAuctionPrice()
    {
        const decimal price = 90m;
        _clock.Now.Returns(new DateTime(2015, 1, 1));

        var result = _auctionService.Accept(_ride.Id, price);

        result.Should().BeFalse();
    }

    [Test]
    public void Auction_rejects_price_when_inactive()
    {
        _clock.Now.Returns(new DateTime(2016, 2, 12, 20, 1, 23));

        var result = _auctionService.Accept(_ride.Id, Arg.Any<decimal>());

        result.Should().BeFalse();
    }

    [Test]
    public void Auction_is_inactive_when_current_time_is_before_auction_startDate()
    {
        _clock.Now.Returns(new DateTime(2016, 2, 12, 18, 0, 23));

        var result = _auctionService.Accept(_ride.Id, Arg.Any<decimal>());

        Assert.IsFalse(result);
    }

    [Test]
    public void Auction_is_active_when_current_time_is_exactly_auction_startDate()
    {
        _clock.Now.Returns(_ride.StartAuction);

        var result = _auctionService.Accept(_ride.Id, _ride.InitialAuctionPrice);

        result.Should().BeTrue();
    }

    [Test]
    public void Action_price_is_valid_at_auction_start_time_if_equal_to_initial_price()
    {
        var price = _ride.InitialAuctionPrice;

        _clock.Now.Returns(_ride.StartAuction);

        var result = _auctionService.Accept(_ride.Id, price);

        result.Should().BeTrue();
    }

    [Test]
    public void Action_price_is_valid_at_auction_end_time_if_equal_to_highest_possible_price()
    {
        var price = _ride.HighestAuctionPrice;

        _clock.Now.Returns(_ride.StartAuction.AddMinutes(60));

        var result = _auctionService.Accept(_ride.Id, price);

        result.Should().BeTrue();
    }

    [Test]
    public void Action_price_is_invalid_if_not_within_time_parameters()
    {
        var price = 12m;

        _clock.Now.Returns(_ride.StartAuction.AddMinutes(30));

        var result = _auctionService.Accept(_ride.Id, price);

        result.Should().BeFalse();
    }

    [Test]
    [Ignore("Uitzoeken hoeveel seconde vertraging wenselijk is")]
    public void Accept_takes_delay_in_requests_into_account()
    {
        var price = 17m;

        _clock.Now.Returns(_ride.StartAuction.AddMinutes(30).AddSeconds(30));

        var result = _auctionService.Accept(_ride.Id, price);

        result.Should().BeTrue();
    }

    [Test]
    public void Ride_is_saved_with_accepted_price()
    {
        var price = 17m;

        var date = _ride.StartAuction.AddMinutes(30);
        _clock.Now.Returns(date);

        var result = _auctionService.Accept(_ride.Id, price);

        Assert.IsTrue(result);

        var dbRide = RavenSession.Load<Ride>(_ride.Id);

        price.IsSameOrEqualTo(dbRide.AcceptedAuctionPrice);
    }

    [Test]
    public void On_Start_Auction_InitialAuctionPrice_should_be_fifteen_percent_of_PriceForCustomer()
    {
        _ride.PriceForCustomer = 100;

        _auctionService.StartAuction(_ride.Id);

        Assert.AreEqual(85m, _ride.InitialAuctionPrice);
    }

    [Test]
    public void On_Start_Auction_send_email_to_priorityPartners()
    {
        var priorityPartner = new Partner { Priority = true, Email = "some@email.com" };

        SetupData(priorityPartner, new Partner { Priority = false });

        _auctionService.StartAuction(_ride.Id);

        _mailer.Received(1).SendAuctionEmail(Arg.Any<string>(), _ride);
    }
}

我有什么（明显的）遗漏吗？这一切的准随机性似乎表明代码没有为每次测试正确重新初始化，但我完全看不出如何。

非常感谢任何帮助。

Answer 1

NSubstitute 缓存来自先前测试的 Arg.Any<...> 调用。先前测试中的错误调用可能会导致出现此神秘错误。

一位了不起的同事向我展示了这个技巧，以找出哪个测试做出了这个错误的调用。

将以下部分放在 Teardown 方法中会导致无效的Arg.Any 调用失败。

    [TearDown]
    public void TearDown()
    {

        var argSpecs = SubstitutionContext.Current.DequeueAllArgumentSpecifications();
        if (argSpecs.Any())
        {
            throw new UnexpectedArgumentMatcherException();
        }
    }

Answer 2

这些行尝试使用带有非替代 (_auctionService) 的参数匹配器：

var result = _auctionService.Accept(_ride.Id, Arg.Any<decimal>());

参数匹配器只能用于替换，不能用于通过new 创建的标准值。